如何在R中用ggplot2制作的图的y轴刻度中准确显示数字的SI前缀？

Question

我有以下图,使用此代码生成

plt <- ggplot(d2, aes_string(x=names(same_df)[1],y= "value")) + 
    geom_point(aes(color = variable), size = 1)+ theme_bw()+
    theme(legend.text=element_text(size=14), legend.title=element_text(size=14))+
    theme(axis.text=element_text(size=20)) +
    theme(axis.title=element_text(size=20,face="bold")) + scale_color_discrete(name = "title", labels = c("1", "2", "3", "4","5","6","7","8","9")) + labs(x = "x", y = "y")+ guides(colour = guide_legend(override.aes = list(size=4),ncol=2,title.hjust=0.5))+theme(plot.margin=unit(c(0,0,0,0),"mm"))

但是我需要在y轴上的数字使用SI前缀表示法,为了得到我做了以下步骤,

library("sos")

在sitools包中使用findFn

findFn("{SI prefix}") 

然后我使用标签中的f2si将浮点数编号转换为带有SI前缀的数字

plt2 <- plt + scale_y_continuous(labels=f2si)

结果情节看起来像这样,

当f2si精确地将y轴改变为-1e ^ -0.8到-10n时,它不能准确地显示0和1e ^ -0.8的值,它们分别为0和10n.有人可以建议在这里应该纠正什么,以便数字显示在它们应该贯穿始终.

谢谢.

Answer 1

我无法重现您的行为。看到这个：

df <- data.frame(x=runif(100), y=(runif(100)-1/2)/1e8)
p <- ggplot(df, aes(x, y)) + geom_point()
p + scale_y_continuous(labels=f2si)

我还发现了另一个类似的功能，如果您不喜欢“0 n”标签：

  format_si <- function(...) {
  # Based on code by Ben Tupper
  # https://stat.ethz.ch/pipermail/r-help/2012-January/299804.html

  function(x) {
    limits <- c(1e-24, 1e-21, 1e-18, 1e-15, 1e-12,
                1e-9,  1e-6,  1e-3,  1e0,   1e3,
                1e6,   1e9,   1e12,  1e15,  1e18,
                1e21,  1e24)
    prefix <- c("y",   "z",   "a",   "f",   "p",
                "n",   "µ",   "m",   " ",   "k",
                "M",   "G",   "T",   "P",   "E",
                "Z",   "Y")

    # Vector with array indices according to position in intervals
    i <- findInterval(abs(x), limits)

    # Set prefix to " " for very small values < 1e-24
    i <- ifelse(i==0, which(limits == 1e0), i)

    paste(format(round(x/limits[i], 1),
                 trim=TRUE, scientific=FALSE, ...),
          prefix[i])
  }
}

p + scale_y_continuous(labels=format_si())